1. Field of the Invention
The present invention relates to a silicon substrate evaluation method, and more particularly to a silicon substrate evaluation method which can prevent a lowering of the yield of semiconductor IC devices.
2. Description of the Related Art
With the recent high-density integration and miniaturization of dynamic random access memories (DRAMs), etc., it has been strongly required to reduce a microscopic warp which occurs in the surfaces of silicon substrates while being processed, as well as crystal defects in the silicon substrates and the surface contamination of the silicon substrates. The techniques for evaluating the microscopic warp, the crystal defects and the surface contamination in advance are needed.
According to one known method for evaluating any crystalline imperfection in a silicon substrate surface, an oxide film is removed after an oxidization process, etching is conducted through the use of an acid selective etchant, and thereafter the pits which have occurred in the substrate surface are detected. According to another known method for evaluating the crystalline imperfection, the half width of the rocking curve, obtained by the X-ray diffraction of the surface layer portion of a silicon substrate, is measured.
However, the crystal imperfection cannot be satisfactorily evaluated by the method adopting the acid selective etchant or the method using the rocking curve obtained by the X-ray diffraction. The presence of the crystal imperfection in the silicon substrate surface cannot be detected until any inconvenience occurs during a semiconductor IC manufacturing process.